File Upload using WebView on Android

main.dart

/// Read details on https://theprogrammingway.com/flutter-file-upload-using-webview-on-android/
import 'dart:io';

import 'package:file_picker/file_picker.dart';
import 'package:flutter/material.dart';
import 'package:webview_flutter/webview_flutter.dart';
import 'package:webview_flutter_android/webview_flutter_android.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  late final WebViewController controller;

  @override
  void initState() {
    controller = WebViewController();
    controller.loadRequest(
        Uri.parse("https://theprogrammingway.com/html-file-upload/"));
    addFileSelectionListener();
    super.initState();
  }

  void addFileSelectionListener() async {
    if (Platform.isAndroid) {
      final androidController = controller.platform as AndroidWebViewController;
      await androidController.setOnShowFileSelector(_androidFilePicker);
    }
  }

  @override
  Widget build(BuildContext context) {
    return WebViewWidget(controller: controller);
  }

  /// Function for file selection from gallery
  Future<List<String>> _androidFilePicker(FileSelectorParams params) async {
    final result = await FilePicker.platform.pickFiles();

    if (result != null && result.files.single.path != null) {
      final file = File(result.files.single.path!);
      return [file.uri.toString()];
    }
    return [];
  }
}

There is nothing special to be done for iOS. The only problem is special configuration required for android.

@Emanoel7S This looks like issue on filepicker, check if you have configured it properly.